Polymers having two or more isocyanate groups per molecule can readily polymerize by a reaction with an active hydrogen containing compound or water, and are widely used in fields such as sealing materials, caulking materials, adhesives, and paints. These isocyanate group-containing polymers are mixed with diamines, amino alcohols, glycols, polyols, etc. and are used as one-part or two-part curing compositions.
Of these, some one-part curing compositions cure in the humidity in the air by the curing mechanism of formula (1): ##STR2## (where R is a divalent organic group).
The carbon dioxide gas produced during the curing gives rise to swelling, foaming, and gas pockets. In particular, in a one-part curing composition with a fast curing speed, gas pockets easily occur inside the cured substance or near the interface between the cured substance and the object to which it adheres, having a detrimental effect on the sealing effect and strength and the adhesion to the object. Further, there is the problem that when the cured substance is heated, foaming, and softening or embrittlement of the cured substance occurs.
To resolve these problems, various proposals have been made in the past. For example, Japanese Examined Pat. Publication (Kokoku) No. 44-2114 discloses the addition of calcium oxide to the composition so as to absorb the carbon dioxide gas produced during curing. Further, Japanese Unexamined Pat. Publication (Kokai) No. 52-17560 discloses the use of a reaction of polyalkylene ether diol and polyalkylene triol with an excess of diisocyanate polymer having equivalent isocyanate groups and the use of a polymer which blocks the remaining isocyanate groups to suppress the foaming due to carbon dioxide gas so as to provide a one-part curing composition with a fast curing no speed. Further, German Pat. No. 2,116,882, No. 2,521,841, No. 2,651,479, and No. 2,718,393 disclose methods for curing without generation of carbon dioxide gas by the addition of enamine or compounds containing an enamine group, an alidimine group, or a ketimine group.
However, the method disclosed in Japanese Examined Pat. Publication (Kokoku) No. 44-2114 suffers from the problem that the generation of carbon dioxide gas under high temperature and humidity conditions exceeds the absorption by the calcium oxide and thus it is difficult to completely prevent foaming due to the carbon dioxide gas. Further, the method disclosed in Japanese Unexamined Pat. Publication (kokai) No. 52-17560 has the defect that foaming occurs under high temperature and humidity conditions and further that the usable isocyanate containing polymers are limited. Further, in the methods disclosed in German Pat. No. 2,116,882, No. 2,521,841, No. 2,651,479, No. 2,718,393, the active hydrogen-containing compounds used are limited to amines and the curing speed is slow. Further, the softening or embrittlement of the cured substance upon high temperature heating is considered to derive from the urethane bonds or urea bonds in the cured substance and, in the case of the use of polyamines or polyols as curing agents, improvement is difficult.